JPH0743832B2 - Tracking controller - Google Patents

Description

The present invention relates to means for stably moving a reading beam from a recording track to another recording track in tracking control of an optical disk reproducing apparatus.

[Prior Art] In a conventional device, a read beam 6 that scans a recording track A formed by a signal pit row as shown in FIG. 2 is moved to an adjacent track C. In that case, the following control was performed. (For example, Japanese Patent Laid-Open No. 54-128707 "Focus Servo Device") First, as shown in the waveform diagram of FIG. 3, the tracking servo open / close signal is set to servo open due to the jump start signal (1), and the illustration is made. Although not shown, when a positive pulse current as shown in FIG. 3 (4) is applied to a drive mechanism (abbreviated as actuator) having a function of physically moving the reading beam tracking device, the actuator obtains thrust. Start moving from the track currently being scanned to another track. Therefore, a tracking error as shown in FIG. 3B occurs at the position where the reading beam moves between tracks. When the reading beam reaches the center position of the positive feedback slope of the tracking servo, the tracking error signal crosses zero at the position B shown in FIG. 2, for example. This zero-cross point is detected by the zero-cross detector, and at the same time as the zero-cross, the servo open / close signal is set to servo close as shown in FIG.
A negative pulse current as shown in (4) is applied to the actuator, and a thrust having a magnitude substantially equal to and opposite in direction to the thrust obtained by the positive pulse current is applied to the actuator for braking. Since the servo has already started to respond, the servo normally retracts on the negative feedback slope. At this time, the tracking error signal is shown in FIG.
As shown in a of item a, there is a residual amount, but it stabilizes for the time being.

As described above, the reading beam 6 has successfully completed the track jump movement from the recording tracks A to C. Also, when jumping in the opposite direction, it can be realized by reversing the polarities of the two pulse currents described above.

[Problems to be Solved by the Invention] In the above-mentioned conventional technique, the loop is completely broken when the first pulse current is applied to the actuator. Therefore, when a DC offset occurs in the drive current of the actuator, DC offset is also lost. This is the case, for example, when playing a disc with a large eccentricity. In such a case, the elastic force generated in the elastic body supporting the actuator is often applied to the actuator. In order to offset this elastic force, a DC offset current cannot be supplied to the actuator during jump movement by the conventional method. If a follow-up residual error occurs in the arm feed mechanism to be moved, there is a problem that the tracking error signal is overshooted as shown by b in FIG. 3 (3).

An object of the present invention is to provide a control means capable of jump control with less overshoot.

[Means for Solving Problems] The purpose of the above is to reduce the high-frequency response of the tracking servo almost at the same time as the jump starts, detect the zero-cross point on the positive feedback slope of the tracking servo, and improve the high-frequency response of the tracking servo. This is accomplished by configuring the timing controller to revert.

[Operation] Next, the operation of the timing controller will be described with reference to the waveform chart of FIG.

In FIG. 4, (1) is a jump start signal, and (2) is a tracking error signal.

First, at the same time as the jump starts, the maximum tracking frequency of the tracking servo characteristic is switched to a frequency lower than the frequency during normal reproduction. This frequency is set low enough to sufficiently attenuate the S-shaped waveform appearing in the tracking error signal at the time of jump. Also, at the same time as the jump starts,
The first pulse current shown in Fig. (4) is applied to the actuator to supply thrust. Next, when the reading beam moves from the first track to the next track, the first zero-cross point of the tracking error that occurs on the positive feedback slope on the line B in FIG. 4 is detected, and this zero-cross detected signal is used. As shown in FIG. 4 (4), the thrust of the actuator is braked by energizing the actuator whose direction is opposite to that of the first pulse current and has the same width.

Therefore, the moving speed of the read beam is attenuated. Then, when the read beam reaches the next track,
The second zero-cross point generated on the negative feedback slope on the line C in the figure is detected, and the maximum tracking frequency of the tracking servo described above is restored to a higher frequency before the jump is started by the signal of this zero-cross detection.

In this way, the tracking servo obtains the original tracking ability on the next track and returns the read beam to the normal reproduction state. Therefore, the timing control is performed by generating the tracking servo characteristic switching signal as shown in FIG.

[Embodiment] Next, one embodiment according to the present invention will be described with reference to the block diagram of FIG.
This will be described with reference to the circuit diagram in the figure and the waveform diagram in FIG. The circuit 100 of FIG. 1 is a tracking error detector,
The tracking error shown in FIG. 4B is generated from the photoelectrically converted reflected light input to 0,120.

The tracking error signal T is input to the phase compensation amplifier 200 whose characteristics can be switched, the loop characteristics of the tracking servo are adjusted appropriately, and the tracking error signal T is supplied to the power amplifier 310 via the adder 300. The amplifier 310 supplies power to the actuator coil 800 and drives the actuator in the disk radial direction to perform tracking control.

The tracking error signal T is supplied to the comparator 400, the signal TE obtained by binarizing the signal T is output from the circuit 400, and is supplied to the first zero-cross detector 410 and the second zero-cross detector 420. The first zero-cross detector 410 is
The result of detecting the zero-cross point on the positive feedback slope of the information track from the tracking error signal T is the kick pulse generator.
Supply to 500. The second zero-cross detector outputs the result of detecting the negative feedback slope of the information track from the tracking error signal T and supplies it to the timing controller 600. Although not shown, the jump start signal output from the system control circuit of the optical disc reproducing apparatus is input to the terminal 520 and supplied to the timing controller 600 and the kick pulse generator 500. From the timing controller 600,
The characteristic switching signal TL ′ shown in FIG. 6 (10) is output and supplied to the phase compensation amplifier 200. Kick pulse generator 5
The kick pulse shown in FIG. 6 (8) is output from 00 and supplied to the power amplifier 310 via the adder 300. These configurations operate as described above,
An example of a specific circuit configuration of the first and second zero-cross detectors 410, 420, the timing controller 600, the kick pulse generator 500, and the amplifier 200 capable of switching the phase compensation characteristic is shown in the circuit diagram of FIG. The operation will be described with reference to the waveform chart of FIG.

In FIG. 5, 502 is a reference signal generator for generating a reference signal of a constant frequency, 503 is an up / down counter, 504
Is an SR-flip-flop, 511 is an E-OR gate, 510,5
13 is a D flip-flop, 509, 512 are inverters, 505, 5
08 and 514 are AND gates, 515 is an element that always outputs "H" level, 506 and 507 are switches, 520 and 202 are operational amplifiers, 203 and 20
6 is RC network, 205 is switch, 204 is capacitor, 52
1,522,523,524 are resistors having the same resistance value.

When the jump start signal JT is input to the set terminal S of the SR flip-flop 504, its output is an enable signal.
EN becomes “H”. The signal EN is input to the counter 503,
Start counting. At this time, the D flip-flop 51
Since the output C of 0 is "L", the output P of the AND gate 505 is the sixth
As shown in Fig. (5), it first becomes "H". The signal P is input to the UP terminal of the counter 503 and starts counting up.

Further, P is supplied to the operational amplifier 520 via the switch 507, and a positive kick pulse KP is output from 520 as shown in FIG. 6 (8). This signal KP is the adder 30 of FIG.
It is introduced to the power amplifier 310 via 0. The signal EN is also introduced into the AND gate 514. Since the D flip-flop 513 is initially reset, its output B is "H", the signal EN becomes "H", and at the same time, the servo characteristic switching signal TL 'output from the AND gate 514 is "H". "It becomes. Signal TL ′
Is supplied to the switch 205 and the switch is closed.

The operational amplifier 202 constitutes a characteristic switching amplifier, and the characteristic determined by the RC network 203, 206 is normally set. However, when the switch 205 is closed, the capacitor 204 is connected to the circuit 20.
It is connected to the feedback circuit of 2 and the high frequency characteristic deteriorates. As a result, the high frequency characteristic of the tracking servo is lowered, and since the kick pulse has already been applied, the reading means starts the jump.

Next, when the reading means moves on the information track, a signal as shown in FIG. 6 (3) appears in the binarized tracking error signal TE.

The polarity of this signal TE is inverted or non-inverted by an E-OR gate 511 by a polarity switching signal FR from a system control circuit (not shown) and is supplied to the clock input of the D flip-flop 510. Here, FR for explanation
Is fixed to "L". Reference numeral 510 is a first zero-cross detector, which is triggered by an edge corresponding to the positive feedback slope of TE to invert the output C to "H". Then, the output P'of the AND gate 508 becomes "H" this time, and 505
Becomes "L".

The signal P'is supplied to the operational amplifier 520 via the switch 506, and the kick pulse KP having the opposite polarity to the one previously output.
Is output as shown in FIG. 6 (8). Therefore, the moving reading means is braked.

The switches 506 and 507 are used to change the direction of the kick pulse according to the polarity switching signal FR.

The signal P'is also introduced to the counter 503 to start down counting. The counter 503 generates an overflow signal UF when the counter becomes 0. This signal UF is introduced to the reset terminal R of the SR flip-flop and the enable signal
Set EN to “L”. Therefore, the counter stops operating and AND
The gates 505 and 508 both set their outputs P and P'to "L".

Therefore, the kick pulse EP is not output. By this operation, the pulse widths of the kick pulse and the pulses in the positive and negative directions become substantially equal.

Here, before the output of the pulse is completed, as shown in FIG. 6 (3), if an edge indicating the zero cross point of the negative feedback slope of the information track appears in the tracking error signal TE,
The second zero-cross detector D flip-flop 513
Is triggered and its output B is "L" as shown in Fig. 6 (9).
become. Therefore, the characteristic polarity signal TL 'becomes "L", the capacitor 204 is disconnected from the operational amplifier 202, the phase compensation returns to the normal state, the tracking servo starts operating, and the reading means is pulled to the target track.

As described above, according to the present invention, the loop is not completely opened at the time of the track jump, only the DC component of the tracking error is transmitted, and the reading means is located just above the target track. The tracking servo starts to turn on when it comes to, so when a follow-up residual error occurs due to the feed mechanism of the reading means, or when a follow-up residual error occurs due to the feed mechanism of the reading means, or when playing a disc with a large eccentricity. Also, there is an advantage that the settling after the jump becomes stable.

[Effects of the Invention] As described above, according to the present invention, the tracking servo can be activated when the reading means is just above the target track, so that the reading means jumps while the DC component is held. At the time of moving, the tracking is settled well after the moving operation, and the overshoot amount of the tracking is reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the features of the present invention, FIG. 2 is an operation principle diagram for explaining a jump operation, FIG. 3 is a waveform diagram for explaining a conventional method, and FIG. 4 is a method according to the present invention. 5 is a circuit diagram showing a specific configuration of an embodiment according to the present invention, and FIG. 6 is a waveform diagram for explaining the operation. [Description of symbols] 100 …… Tracking error detector 200 …… Phase compensation characteristic variable amplifier 400 …… Comparator 410 …… First zero-cross detector 420 …… Second zero-cross detector 500 …… Kick pulse generator 600 ...... Timing controller

Front page continuation (72) Yoshio Miura, Yoshio Miura, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Home Appliances Research Laboratory, Hitachi, Ltd. (72) Hiroyuki Matsushima, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Incorporated (56) References JP 62-6445 (JP, A)

Claims (1)

[Claims] 1. A tracking control device of a disk reproducing device, wherein a reading means for reproducing recorded information from an information track recorded on a rotating disk controls the reading means so as to follow the information track correctly. A tracking error detecting means for generating a tracking error signal corresponding to a position error between the reading means and the information track, and a tracking error signal from the error detecting means are inputted, and a phase delay is advanced and output. Phase delay / advance compensation circuit means, timing signal generating means for generating and outputting a timing signal for causing the information reading means to jump to an adjacent track on the basis of the error signal from the tracking error signal detecting means, At least in the tracking servo loop, and The forward / lead compensation circuit means includes an operational amplifier, a first RC network including an input of the output of the tracking error detection means and a resistor and a capacitor connected to the input side of the operational amplifier, and the operational amplifier. A second RC network composed of a resistor and a capacitor connected between the input side and the output side as the feedback impedance of, and a series connection of a capacitor and a switch connected in parallel to the second RC network. A connection circuit, and during the operation of the reading means to follow a normal recording track, the phase delay / phase delay is generated by the output of the timing signal generating means while the switch forming the series connection circuit is turned off. The output of the timing signal generating means during the period in which the lead compensating circuit means is operated and the reading means makes a track jump to the adjacent track. Therefore, by turning on the switch forming the series connection circuit, the phase delay / advance compensation circuit means is operated in the low-pass filter mode, and the high frequency component contained in the error signal flowing through the tracking servo loop is attenuated. A tracking control device characterized in that tracking control is performed in a closed state.